Colloidal aluminum hydroxide and method of making the same



Patented May 15, 1934 I 1,958,710

UNITED STATES PATENT OFFICE COLLOIDAL ALUMINUM HYDROXIDE AND METHOD OF MAKING THE SAME Paul S. Meyer, Lake Forest, 111.

. No Drawing. Application March 23, 1933,

Serial No. 662,229

9 Claims. (Cl. za -141) The present invention relates to a novel type thermore,- the colloidal properties of the resultof aluminum hydroxide having pronounced colant aluminum hydroxide. gel are much -more loidal properties, and to the process of producpronounced, as in many cases aluminum hying the same. droxide precipitated from an aluminum salt One of the objects of the invention is to form by means of alkalies is not at all colloidal aluminum hydroxide in suspension in the pres-- nor gelatinous. ence of an activating agent which allows the In its preferred embodiment, the present ready filtration, of the product, so that it may invention depends upon the reaction between be separated to some extent from the mother sodium aluminate and'aluminum sulfate. For

liquor from which it is precipitated. and which examp e. n producing the aluminum hydroxide,

will allow the washing therefrom of impurities one pro e s by dissolving O e v el 10 lb resulting from the reaction by which it is of aluminum sulfate (A12(SO4):.18H:0), in 48 formed. gallons of water, and in another vessel 16 lbs. of

A further object of the invention is the prepaa o u a um ate s0llltl0n i 48 gallons 0f 15 ration of aluminum hydroxide from sodium water. The said SOdium aluminate solution is aluminate and a. soluble aluminum salt. a commercialproduct produced by the National A further object of the invention is to form Aluminate p r ion. of C c Illinois, aluminum hydroxide in colloidal form by intero isti g o a I aque us s lution of sodi action between sodium aluminate and a soluble meta-aluminate, i z i, containing a sli 2' aluminum salt, and thereupon treating the excess of sodium hydroxid the Composition Ol product precipitated by the reaction with an said solution being ally 32% NazAlzoi. alkaline earth hydroxide, preferably calcium. H nd the balance water. Whenever hydroxide, which greatly enhances the filterasodium aluminate is mentioned in the present bility of the precipitated colloidal aluminum application. this yp f sodium aluminate is 25 hydroxide. understood as being the preferred form. How- Further objects of the invention will appear ever. a qu a a u t O d y so from the detailed description and claims herealuminate d V d in walls! y be llsed- The inbelow. 7 two solutions prepared as above, are mixed The fundamental principle involved in the with a t it being im a as to which 30 present inventionisthe production of aluminum is P o After the mixing has hydroxide from two reagents, both of i h taken place, and as soon thereafter as convencontain aluminum as a component; one of them lent, -2 85 lbs. of calci hydroxide, -CMOH) 2, carrying the aluminum as an acid radical and made o a S u y habout'two gallons of the other as a metallic ion. Thus, in the final Water, are stirred iIlt th mixture 0 the two 85 product, the only other material formed will be solutions. whereupon the entire mixture is asalt, which is readily removed from the preallowed to remai q s a period Of cipitated aluminum hydroxide by washing. In from six t twelve u sthis respect the present invention differs essen- In order to avoid contamination of the prodtially from the hitherto employed means for uct and its discoloration by iron salts, it is pre- 40 the production of aluminum hydroxide, for in ed t at e c o take place in Wooden the past the process of preparing this material containers, or, still more preferable, in tanks has usually been predicated upon the precipiaving a v ous olflg liningtation of a soluble aluminum salt, such, for After the mixture is allowed to stand for from example, as aluminum sulfate with an alkali, six to twelve hours, it will be found that it con- 45 such as sodium carbonate, ammonium hydroxsists of a jelly-like mass of colloidal aluminum ide and the like. Aluminum hydroxide has, hydroxide which can readily be'filtled moreover, also been precipitated from sodium examp on lota y filte Of'the p known aluminate by the addition of .an acid-and by as the Oliver in or upon which filter the passing carbon dioxide gas into the aluminate colloidal precipitated aluminum hydroxide is 50 solution. The present invention, however, obwashed with water to remove the soluble salts tains aluminum hydroxide from both the roluble formed, which in the present case will be sodium aluminate and a soluble aluminum salt. Thus sulfate. The above proportions will yield about the greatest possible economy is secured, and lbs. of the aluminum hydroxide gel, 00!!- the production of the aluminum hydroxide is taining from 4'to 10% of solids.

rendered both simple and inexpensive. Fl.-- The reaction that takesplace is one of metathesis, the aluminum from the aluminum sulfate, as well as from the sodium aluminate appearing as aluminum hydroxide in the product, the only other product being sodium sulfate and the slight amount of sodium hydroxide which remains unchanged.

It has been found advisable, although not strictly essential, to control the hydrogen ion concentration of the precipitated mass so that it will be slightly on the alkaline side, say, between pH 7.5 and 9.0, and for the best results at approximately pH 8.0.

It is not known at the present time just what the effect of the calcium hydroxide is, but it has been proved by experiment and large-scale operations that the calcium hydroxide has a tremendous effect upon the filterability of the precipitated colloidal aluminum hydroxide, for in the'absence of the calcium hydroxide the aluminum hydroxideprecipitated is so diflicult to filter as to render its purification and theremoval therefrom of the formed soluble salts almost impossible. Therefore, a great step of advancement has been made in the present process by the use of the calcium hydroxide. Whether this material plays a part in the reaction itself has not been definitely established, but the fact remains that it greatly enhances the colloidal properties as well as the filterability of the desired end product.

Experiments have shown that strontium hydroxide and barium hydroxide may be substituted for the calcium hydroxide, but the results will be very mediocre. Calcium almuinate is also effective in modifying the fllterability of the aluminum hydroxide but by no means to as great an extent as calcium hydroxide. Barium aluminate is-practically ineil'ective for the purpose.

"It has also been discovered: that the use of sodium carbonate, sodium hydroxide, or ammonium hydroxide as precipitants for aluminum hydr xide from aluminum is not effective for producing a illterable aluminum hydroxide which can be purified by washing, and therefore aluminum hydroxide made by such precipitation does not fall within the scope of the precipitated from aluminum sulfate by the just enumerated alkalies is pasty and very diflicult to filter.

The aluminum hydroxide in its colloidal form, after being washed, will be found to contain as little as 1% of sodium sulfate, and, despite the fact that it may contain as high as 96% of water, appears in the form of a substantially solid substance which can be packed in waxed wooden or waxed cardboard containers without much absorption of water. by the container.

The colloidal aluminum hydroxide prepared in accordance with the present invention is a very valuable substance and lends itself particularly to the manufacture of printing inks, for the coating and sizing of paper as a substitute for satin-white-which it greatly exceeds in value from a paper-coating standpoint-and to any other use where a colloidal aluminum hydroxide may be indicated for employment in the arts.

The fundamental concept of the present invention, therefore, comprises the employment In the hereunto appended claims, the term activating agent is understood to cover such compounds as calcium hydroxide, strontium hydroxide, barium hydroxide, calcium aluminate, and their chemical equivalents.

What it is desired to protect by Letters Patent is as follows:

1. A colloidal precipitated aluminum hydroxide characterized by its gelatinous nature and containing from 4% to 10% of total solids, being in the form of a gelatinous solid having high absorptive qualities. 7 I

2 Aluminum hydroxide in gelatinous colloidal form containing small amounts'of a substance from the group consisting of calcium, strontium and barium hydroxides and calcium aluminate.

3. The process of producing colloidal readily filterable aluminum hydroxide which comprises mixing solutions of sodium aluminate and a soluble aluminum salt to form aluminum hydroxide and mixing said aluminum hydroxide in ,solution with a substance selected from the group consisting of calcium hydroxide, strontium hydroxide, barium hydroxide and calcium aluminate.

4. The process of producing colloidal readily filterable precipitated \aluminum hydroxide which comprises mixing a solution of sodium aluminate with a solution of aluminum sulphate to form precipitated aluminum hydroxide and adding to said precipitated aluminum hydroxide a suspension of calcium hydroxide, and filtering the resultant insoluble product.

5. The process of producing colloidal readily filterable' precipitated aluminum hydroxidewhich comprises mixing a solution of sodium aluminate with a solution of aluminum sulphate to form precipitated aluminum hydroxide and adding to said precipitated aluminum hydroxide a suspension of calcium hydroxide, filtering the resultant insoluble product and washing the same.

6. The process of producing colloidal readily filterable aluminum hydroxide which comprises mixing solutions of sodium aluminate, aluminum sulphate and a suspension of calcium hydroxide, allowing interaction between the enumerated substances to take place, whereby aluminum hydroxide is precipitated in filterable form, and filtering said precipitate and washing the same.

7. The process of producing colloidal aluminum hydroxide which comprises dissolving aluminum sulphate and sodium aluminate in separate quantities of water, suspending calcium hydroxide in a third separate quantity of water, mixing the solutions of sodium aluminate and aluminum sulphate, thereupon adding the suspension of calcium hydroxide,'allowing the re.- sulting mixture to stand quiescent for a period of from 6 to 12 hours, and thereafter filtering the .resulting precipitate and washing the same.

8. A colloidal" precipitated aluminum hydroxide gel containing from 4% to 10% of total solids, being in the form of a gelatinous solid having high absorptivequalitiesfand containing a small amount of a substance from the group consisting of calcium, strontium and barium hydroxides and calcium aluminate.

9. A colloidal precipitated aluminum hydroxide gel containing from 4% to 10% of total solids, being in the form of a gelatinous solid having high absorptive qualities, and containing a small amount of calcium hydroxide.

PAUL s. MOYER. 

